We will test the efficacy and safety of a new antiviral drug, lobucavir, from Bristol Myers Squibb, in immunocompetent subjects with recurrent herpes labialis infections. Volunteers in this randomized, double-blind, placebo-controlled study will received one of two active doses of lobucavir or placebo twice daily for five days. Follow-up visits to the clinic will continue until the lesions are completely healed. Lobucavir has proven a potent antiviral in tissue culture and animal model studies. Therefore, the findings from these studies may help in developing a treatment that will hasten healing of lesions and reduce the severity or duration of the pain and discomfort associated with the infection.